The present invention relates generally to facsimile data communication equipment and, more particularly, to a method for enabling certain data communication equipment, such as a facsimile modem, to transmit in a more reliable fashion serial data from data terminal equipment to facsimile equipment. Data terminal equipment includes, for example, a computer that may, in some instances, be interconnected to a network. Data communication equipment includes, for example, a facsimile modem board that may be interconnected between the computer and a communication medium, such as a telephone line.
The data terminal equipment and data communication equipment must work in harmony to delivery data over the medium to a facsimile machine. Technical standards that allow such equipment to deliver and receive facsimile data have been developed by the Electronics Industry Association (EIA), Telecommunications Industry Association (TIA), and International Consultative Committee on Telephony and Telegraphy (CCITT).
Unfortunately, even upon following such standards, transmissions of message data may be unintentionally aborted. Much data terminal equipment has a single central processing unit ("CPU") or a limited number of CPUs, such that a single CPU, or server CPU, must alternate between doing different tasks. Thus, for example, a driver or controller for a CPU may periodically "interrupt" the CPU from overseeing the transmission of message data from memory to the facsimile modem, where the message data may be sent, via the telephone line, to a facsimile machine. In some cases, a relatively long time elapses from when the CPU stops transferring data from memory to the facsimile modem to when the CPU finishes its alternative tasks and resumes sending data to the facsimile modem.
Such a delay in sending information to the facsimile modem, and, thus, to the facsimile machine, may cause the facsimile machine to "time out." In such a case, the facsimile machine may respond as though the communication link between the facsimile modem and facsimile machine has been severed and terminate the communication link.
The inability of data terminal equipment to transmit data to the data communication equipment fast enough to meet the requirements of the facsimile equipment is aggravated when the data terminal equipment is part of a computer network and controlled by a network driver. The driver may well clear the data terminal equipment interrupts for more than the period required to serially send a character to the data communication equipment. The facsimile machine may interpret the silence, or cessation of the message data stream, as meaning that the transmission has been aborted.
As a result, many transmissions are unnecessarily aborted. An operator may understandably become annoyed upon having to "redial" the facsimile machine and reestablish the communication link to the facsimile machine each time that the data terminal equipment controller interrupts the CPU for too long a period.